Fluorescent molecular rotors (FMRs) can act as viscosity sensors in various media including subcellular organelles and microfluidic channels. In FMRs, the rotation of rotators connected to a ...fluorescent π‐conjugated bridge is suppressed by increasing environmental viscosity, resulting in increasing fluorescence (FL) intensity. In this minireview, we describe recently developed FMRs including push–pull type π‐conjugated chromophores, meso‐phenyl (borondipyrromethene) (BODIPY) derivatives, dioxaborine derivatives, cyanine derivatives, and porphyrin derivatives whose FL mechanism is viscosity‐responsive. In addition, FMR design strategies for addressing various issues (e.g., obtaining high FL contrast, internal FL references, and FL intensity‐contrast trade‐off) and their biological and microfluidic applications are also discussed.
Spinning around: This minireview discusses recently developed fluorescent molecular rotors (FMRs), which act as viscosity sensors in various media including subcellular organelles and microfluidic channels. In addition, the mechanism of viscosity‐responsive fluorescence, design strategy of FMRs for addressing remarkable issues, and their various biological and microfluidic applications, are also discussed.
Efficient broadband organic terahertz (THz) generators using X‐shaped alignment of the nonlinear optical chromophores, as an alternative to the parallel alignment of chromophores in benchmark organic ...crystals, are reported. All the developed six organic benzothiazolium crystals exhibit an isomorphic X‐shaped alignment of chromophores, resulting in an unprecedentedly large off‐diagonal optical nonlinearity (>100 × 10−30 esu), which presents one of the largest off‐diagonal optical nonlinearity of organic crystals. The benzothiazolium crystals exhibit efficient broadband THz wave generation employing the off‐diagonal optical nonlinearity, in contrast to the present state‐of‐the‐art organic THz generators that mostly utilize diagonal optical nonlinearity. For using off‐diagonal and diagonal optical nonlinearities, the polarization of the optical pump is perpendicular and parallel, respectively, to the polar axis of crystals. In addition to a large THz wave generation efficiency with one order of magnitude higher peak‐to‐peak THz electric field than that generated in a 1.0‐mm‐thick inorganic benchmark ZnTe crystal, the benzothiazolium crystals generate broadband THz spectra with an upper cut‐off frequency of near 8 THz, and the absence of strong absorption dimples in the range of 0.5−4 THz. Therefore, the X‐shaped alignment of chromophores presents an interesting potential alternative for efficient broadband organic THz generators.
X‐shaped alignment of nonlinear optical chromophores that results in unprecedentedly large off‐diagonal optical nonlinearity offers a potential alternative for efficient broadband organic THz generators, in contrast to the present state‐of‐the‐art organic THz generators that mostly employ diagonal optical nonlinearity from the parallel alignment of chromophores.
New molecular salt crystals based on linear‐shaped polymer‐like cation–anion assembly exhibiting extremely large nonlinear optical response and high THz generation efficiency are reported. Two ...hydroxy benzothialzolium PMB (2‐(4‐(4‐(hydroxymethyl)piperidin‐1‐yl)styryl)‐3‐methylbenzodthiazol‐3‐ium) crystals with different benzenesulfonate counter anions provide isomorphic crystal structure with acentric monoclinic Cc space group symmetry. In contrast to previously reported benchmark nonlinear optical salt crystals with a parallel‐type cation–anion assembly, newly developed PMB‐based crystals exhibit a series‐type cation–anion assembly mediated by strong bidentate‐like hydrogen‐bonds. Such series‐type cation–anion assembly results in perfect alignment of highly nonlinear PMB cations in the crystalline state, leading to extremely large diagonal component of the second‐order nonlinear optical coefficient exceeding that of the state‐of‐the‐art nonlinear optical crystals. In THz wave generation experiments based on optical rectification, a 0.33 mm thick PMB crystal generates intense THz pulses with peak‐to‐peak THz electric field of 430 kV cm−1 and extremely broad flat spectrum with upper cut‐off frequency of above 8.0 THz. In addition, compared to inorganic standard 1.0 mm thick ZnTe crystals, the PMB crystal delivers a 24 times higher THz electric field and about 3 times broader bandwidth. Therefore, hydroxy benzothialzolium PMB crystals are highly desired novel materials for various nonlinear optical applications including THz photonics.
New hydroxy benzothialzolium molecular salt crystals based on a series‐type cation–anion assembly mediated by strong bidentate‐like hydrogen‐bonds, in contrast to previously reported benchmark nonlinear optical salt crystals with a parallel‐type cation–anion assembly, exhibit extremely large nonlinear optical response and high THz wave generation efficiency.
Enhanced terahertz (THz) wave generation is demonstrated in nonlinear organic crystals through refractive index engineering, which improves phase matching characteristics substantially. Unlike ...conventional low‐bandgap nonlinear organic crystals, the newly designed benzimidazolium‐based HMI (2‐(4‐hydroxy‐3‐methoxystyryl)‐1,3‐dimethyl‐1H‐benzoimidazol‐3‐ium) chromophore possesses a relatively wide bandgap. This reduces the optical group index in the near‐infrared, allowing better phase matching with the generated THz waves, and leads to high optical‐to‐THz conversion. A unique feature of the HMI‐based crystals, compared to conventional wide‐bandgap aniline‐based crystals, is their remarkably larger macroscopic optical nonlinearity, a one order of magnitude higher diagonal component in macroscopic nonlinear susceptibility than NPP ((1‐(4‐nitrophenyl)pyrrolidin‐2‐yl)methanol) crystals. The HMI‐based crystals also exhibit much higher thermal stability, with a melting temperature Tm above 250 °C, versus aniline‐based crystals (116 °C for NPP). With pumping at the technologically important wavelength of 800 nm, the proposed HMI‐based crystals boost high optical‐to‐THz conversion efficiency, comparable to benchmark low‐bandgap quinolinium crystals with state‐of‐the‐art macroscopic nonlinearity. This performance is due to the excellent phase matching enabled by decreasing optical group indices in the near‐infrared through wide‐bandgap chromophores. The proposed wide‐bandgap design is a promising way to control the refractive index of various nonlinear organic materials for enhanced frequency conversion processes.
Newly designed benzimidazolium‐based crystals based on the so‐called wide‐bandgap approach allow efficient terahertz (THz) wave generation pumped at near‐infrared wavelengths near 800 nm due to substantially improved phase matching between optical and THz waves distinct from other benchmark organic nonlinear optical crystals.
Invited for the cover of this issue is the collaborative work of the groups of O‐Pil Kwon (Ajou University), Chang‐Lyoul Lee (Advanced Photonics Research Institute, APRI/Gwangju Institute of Science ...and Technology, GIST), and Sehoon Kim (Korea Institute of Science and Technology, KIST). The cover image illustrates the viscosity‐sensitive fluorescent behavior of fluorescent molecular rotors (FMRs) in various viscous media. The intensity of the FMRs increases with decreasing speed of the rotor; this is portrayed as the waterwheel in the cover image. When the waterwheel slowly rotates in winter (high viscosity media), FMR—portrayed as the house in the image—shows strong fluorescent‐light illumination (left‐hand side of the image). In contrast, the right‐hand side of image depicts decreasing fluorescence intensity with increasing rotation of the waterwheel (low viscosity media). Read the full text of the article at 10.1002/chem.201801389.
“Fluorescent molecular rotors have excellent potential for measuring and imaging microviscosity in various organelles under in vivo and in vitro conditions and in various microfluidic channels.” Read more about the story behind the cover in the Cover Profile and about the research itself on page 13706 ff. (DOI: 10.1002/chem.201801389).
Without stimuli, hair cells spontaneously release neurotransmitter leading to spontaneous generation of action potentials (spikes) in innervating afferent neurons. We analyzed spontaneous spike ...patterns recorded from the lateral line of zebrafish and found that distributions of interspike intervals (ISIs) either have an exponential shape or an "L" shape that is characterized by a sharp decay but wide tail. ISI data were fitted to renewal-process models that accounted for the neuron refractory periods and hair-cell synaptic release. Modeling the timing of synaptic release using a mixture of two exponential distributions yielded the best fit for our ISI data. Additionally, lateral line ISIs displayed positive serial correlation and appeared to exhibit switching between faster and slower modes of spike generation. This pattern contrasts with previous findings from the auditory system where ISIs tended to have negative serial correlation due to synaptic depletion. We propose that afferent neuron innervation with multiple and heterogenous hair-cells synapses, each influenced by changes in calcium domains, can serve as a mechanism for the random switching behavior. Overall, our analyses provide evidence of how physiological similarities and differences between synapses and innervation patterns in the auditory, vestibular, and lateral line systems can lead to variations in spontaneous activity.
The side setback areas of buildings are generally underutilized urban spaces. Often, they are used as unauthorized commercial spaces, which lead to legal struggles and safety and sanitation hazards. ...However, the presence of these establishments implies a demand for using these spaces, and many argue that such structures enhance and vitalize cities. This study establishes a new direction for utilizing side setback areas that harmoniously meets the demands of city dwellers and business owners while ensuring safety and compliance with regulations. We examined the utilization status of 371 side setback areas in various districts of Seoul and surveyed 20 urban management experts. Th results indicate that at least 30% of all buildings in the study repeatedly violated laws regarding the use of their side setback spaces, and 100% of the experts agreed that the current regulatory system is inflexible. Our analysis suggests that reform is needed and offers tangible guidelines so that these generally underutilized spaces may become useful when safety and sanitation requirements are met. In the context of overpopulated urban spaces, side setback areas can be repurposed to meet the needs of urban residents while ensuring safety and sanitation.
Hepatocellular carcinoma (HCC) is a highly aggressive form of liver cancer with poor prognosis. The lack of reliable biomarkers for early detection and accurate diagnosis and prognosis poses a ...significant challenge to its effective clinical management. In this study, we investigated the diagnostic and prognostic potential of programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expression in peripheral blood mononuclear cells (PBMCs) in HCC. PD-1 and CTLA-4 gene expression was analyzed comparatively using PBMCs collected from HCC patients and healthy individuals. The results revealed higher PD-1 gene expression levels in patients with multifocal tumors, lymphatic invasion, or distant metastasis than those in their control counterparts. However, conventional serum biomarkers of liver function do not exhibit similar correlations. In conclusion, PD-1 gene expression is associated with OS and PFS and CTLA-4 gene expression is associated with OS, whereas the serum biomarkers analyzed in this study show no significant correlation with survival in HCC. Hence, PD-1 and CTLA-4 expressed in PBMCs are considered potential prognostic biomarkers for patients with HCC that can facilitate prediction of malignancy, response to currently available HCC treatments, and overall survival.
Recently developed fluorescent molecular rotors (FMRs) acting as viscosity sensors in various media, such as biological and microfluidic environments, are described in the Minireview by C.‐L. Lee, S. ...Kim, O‐P. Kwon et al. on page 13706 ff. They describe the design strategy for various FMRs including push–pull type π‐conjugated chromophores, meso‐phenyl (borondipyrromethene) derivatives, dioxaborine derivatives, cyanine derivatives, and porphyrin derivatives. In addition, remarkable issues and the applications of FMRs are also described.
In article number 1901921, Mojca Jazbinsek, Fabian Rotermund, O‐Pil Kwon and co‐workers report the X‐shaped alignment of nonlinear optical chromophores exhibiting unprecedentedly large off‐diagonal ...optical nonlinearity. This offers a potential alternative for efficient broadband organic THz generators.
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